1. Field of the Invention
The invention relates to a chain cover that covers a timing chain for transmitting the rotation of a crankshaft of an internal combustion engine to a camshaft, the chain cover having reinforcing ribs on the inside thereof.
2. Description of the Related Art
An example of this type of chain cover is described in Japanese Patent Application Publication No. 10-220684 (JP-A-10-220684). This chain cover is provided with a first rib formed to extend downward from a middle portion to an outer peripheral portion of the chain cover, and a second rib formed to extend downward from an outer peripheral portion to a middle portion.
However, lubrication oil for lubricating a timing chain and lubrication oil and the like discharged from a hydraulic tensioner for adjusting the tension of the timing chain, are dispersed and adhere to the inner wall of the chain cover.
Lubrication oil that has adhered to the inner wall of the chain cover in this manner flows downward along the inner wall and when it reaches the first rib and the second rib, flows onto the upper surfaces of each of these ribs. Here, lubrication oil that has reached the first rib formed to extend downward from a middle portion to an outer peripheral portion flows in the direction of the outer peripheral portion of the chain cover due to the first rib, while lubrication oil that has reached the second rib formed to extend downward from an outer peripheral portion to a middle portion flows in the direction of the middle portion of the chain cover due to the second rib.
In this manner, lubrication that has flown in the direction from the middle portion to the outer peripheral portion of the chain cover subsequently returns to an oil pan without contacting the timing chain even it drops below the chain cover.
On the other hands lubrication oil that has flown from the outer peripheral portion to the middle portion of the chain cover drops downward from the middle portion of the chain cover, and ends up contacting the timing chain rotating around a crankshaft. In this manner, if the lubrication oil contacts the timing chain while it is rotating, air bubbles easily enter the lubrication oil, thereby leading to, for example, a decrease in hydraulic pressure of the lubrication system or an inadequate supply of lubrication oil.